Sargassum crabs, Portunus sayi, are distributed in the western Atlantic Ocean and the Caribbean Sea. They are a fairly common species to encounter during blackwater dives in Florida, especially in the summer months when floating Sargassum seaweed patches are more abundant. They tend to be very active around the lights of the downline, diving to surprising depths and hunting various prey that are also attracted to the lights.

Even though they are common, this was only the second time I had ever encountered a mated pair. Besides being a rare find, they are also very active, constantly swimming and spinning in circles, which makes it a challenge to photograph them easthetically. Fortunately, this pair paused long enough to allow me to snap a quick portrait before spinning down into the depths beyond my reach.